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Discussion Starter · #1 · (Edited)
{EDIT: Wrong error code. Should be P2198, not P2168}

O2 SENSOR 21 output is sluggish and stays near 0.5V, compared to,
O2 SENSOR 11 output moves faster and goes deeper in peaks and valleys.

This sensor was replaced 3 years and 30k miles ago. New spark plugs at the same time.

Fuel trim numbers are 1-3%. ST and LT add up to 5% or less. No difference between bank 1 and bank 2. So I am not injecting excessive fuel to bank 2.

If bank 2 is REALLY rich (not faulty wiring or sensor), it's gotta be incomplete combustion. How can I tell? What scan tool test will show it? Thanks.

2005 Vulcan 130k miles, car starts/idles/accelerates normal.
 

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What type of replacement sensor was used? It may well have gone bad again. Front ones also go bad first because they get dirty. Any oil or contamination on the outside of the sensor will cause them to fail eventually (they compare oxygen levels to outside the exhaust). Since a new sensor is only $40, it is an easy first start (use a Motorcraft DY-1039 one).

If you have incomplete combustion, you will have a misfire and it will idle poorly. You can also pull the spark plugs and read them. Finally, you can do a power balance test (unplug the spark plugs one at a time and listen for a change in the idle).

Did you do the "goose" test? The sensor should go lean (0v) when you blip the throttle. Does the sensor start switching at higher rpm (2500+?). Watch this video:
 

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Discussion Starter · #3 ·
1) Used Bosch 3 years and 30k miles ago.
2) Thanks for the video. Did a little more reading on internet and learned that O2 sensor switching frequency stays the same even in rich engine. Just the avg is pushed higher. Mine is sluggish. It will be replaced.
3) Thanks for the power balance test. Is there a course/video on how to use a scan tool?
 

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Discussion Starter · #4 ·
Well, P2198 disappeared after a good 10+ mile trip from work. Though sensor output is not peaking and valleying as much as the bank 1 counterpart, its frequency is as good as the other. At this point, I will continue to monitor.

Checked all Bank 2 spark plugs. No indication of rich burn (soot, black, etc).

Just P0430 remains, cat converter 2 below efficiency below threshold. I have lived with it.

Thanks.
 

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If the sensor isn't hitting threshold voltages, even though it's cycling correctly the computer might not be able to lock onto the signal. It has to cross 0.45 V to be counted. If the sensor’s output voltage never gets higher than 0.60 V and never drops to less than 0.30 V, it needs to be replaced. It should be hitting 0.20 to 0.80 volts at the extremes.

Since you have P0430, you might take a look at the rear O2 sensor output (O2 SENSOR 22). If the catalyst is working, the voltage really shouldn't really cycle that much compared to the upstream sensor (maybe a few times a minute). If it seems to cycle in step with the upstream sensor, then your catalyst is bad. But there's a chance P0430 could be caused by the bad oxygen sensor(s). Rear sensors should operate under the same voltage ranges and transition times as the front sensors, so you might check them out while you're at it. Reset the codes and see if it comes back.

Great article on reading O2 sensors: BAT Auto Technical-Professional mechanics giving advice-An Educational Site w/ OBD2 Trouble Codes and Technical info & Tool Store.

Since you were able to get the codes, check the fuel trims, and monitor the O2 sensors, it seems like you have a pretty good handle on running the scan tool. But here's a video showing the basics:
On more advanced OBDII scan tools (maybe you have one), you can actually view graphs of live data like the O2 sensor voltages, airflow, throttle position, timing advance, etc. On the really expensive scan tools (dealer grade), you can monitor everything right down to window switches (including the ABS, Airbag, and transmission modules). If you have more Q's just post back or PM.

You have great FT's, good reading plugs, and the engine runs fine. Unless you notice something else I'd say the engine is running great. I guess you can replace the sensor at your convenience if you feel it is still bad and the CEL is burning a hole in your peripheral vision!

Tip: Cars are happiest if they're driven 30 min or more at least once a month. People that live in cities sometimes have trouble with this and they get more than their fair share of emissions problems.
 

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Discussion Starter · #6 ·
B2S1 output crosses 0.45 V back and forth but doesn't hit low (0.2V) or high (0.8V), exactly as you explained. I am now convinced I need a new O2 sensor. I will tackle P0430 after that.

Thanks for the link. It helped me how to read O2 sensor output correctly.

I just bought a PC-based scan tool, AutoEnginuity Ford bundle. My Ford pickup had an EVAP code. Relying on OBDII code was too time consuming and frustrating. I had to buy a scan tool to read the sensors directly.

This new tool will be a very useful device if I know how to use it right. I am looking for a book or a video that will teach me how to make more out of a scan tool.

I ran power balance test yesterday first time. All cylinders were contributing equally. Good learning experience.
 

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I "lived" with P0430 for a whole year thinking that I need new cat. But I bite the bullet and replaced the upstream o2 sensor on offending bank (the one towards radiator) and code dissapeared - for a few months now.

I used a Bosch sensor from Amazon. Now my LT fuel trims are different, I guess the other sensor is not so good in response either. But is harder to get to...

I have a bluetooth scanner that I can read in real time with my Android (Torque).
 

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I just bought a PC-based scan tool, AutoEnginuity Ford bundle. My Ford pickup had an EVAP code. Relying on OBDII code was too time consuming and frustrating. I had to buy a scan tool to read the sensors directly.

This new tool will be a very useful device if I know how to use it right. I am looking for a book or a video that will teach me how to make more out of a scan tool.

I ran power balance test yesterday first time. All cylinders were contributing equally. Good learning experience.
Wow, I was looking at those AutoEnginuity tools and they look really nice. They're expensive, but I guess you had a good reason to buy one. I also see you can do a power balance test with them (without even opening the hood!), so I guess I was wondering if you used the scan tool or did it the low-tech way (unplugging plugs or injectors)? Will it just tell you what cylinder(s) are bad or do you actually get a Δ rpm graph for each one? It looks like you can also manually command the spark advance as well as actuate the EGR and IAC valves for testing. Looks like you can also bleed the ABS unit as well. I think there are at least a few people here that would like to get their hands on one of these for a day! Cool tool! :D

I went the budget route and got an OBDLink SX for $50. It doesn't do all the fancy stuff yours can, but it will do everything OBDII-related quite well. You can buy Ford add-on software for it so you can read ABS, EVAP, etc. but it isn't a two-way scan tool like the AutoEnginuity so I can't actuate stuff or do a power balance with it.
 

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Discussion Starter · #9 ·
1) Power balance test actually gives delta rpm for each cylinder. I didn't disconnect plugs and injectors. Is this the pseudo-compression test that shops do without a pressure gauge? Or is there something else?

2) I don't have the knowledge to fully utilize the tool yet. But I already solved an EVAP code. Some members report replacing multiple parts and still having the same trouble. I wonder if a scan tool would be more cost effective than guessing the faulty part. Though not fully skilled myself with the tool yet, I can easily recommend a scan tool to anyone who maintains multiple cars for his family. I should have bought one years back when I first had 4 cars in my driveway.

3) Please help me select the right oxygen sensor. I used to think oxygen sensors are different only in the lead wire length. Actually, there are universal oxygen sensors that you can use for both banks, both up- and downstream.

I am looking for a genuine Ford part. One website says xxx-9G444-xxx is the upstream sensor. Another website says xxx-9F472-xxx. Even another website says "green plug" for Flex fuel (which is mine). Rockauto lists 3 different kinds (DY-1038, -1039, -1040). Reply from Rockauto to my email didn't help. Which one is for me? OEM is 11". Thanks.
 

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1) Power balance test actually gives delta rpm for each cylinder. I didn't disconnect plugs and injectors. Is this the pseudo-compression test that shops do without a pressure gauge? Or is there something else?

2) I don't have the knowledge to fully utilize the tool yet. But I already solved an EVAP code. Some members report replacing multiple parts and still having the same trouble. I wonder if a scan tool would be more cost effective than guessing the faulty part. Though not fully skilled myself with the tool yet, I can easily recommend a scan tool to anyone who maintains multiple cars for his family. I should have bought one years back when I first had 4 cars in my driveway.

3) Please help me select the right oxygen sensor. I used to think oxygen sensors are different only in the lead wire length. Actually, there are universal oxygen sensors that you can use for both banks, both up- and downstream.

I am looking for a genuine Ford part. One website says xxx-9G444-xxx is the upstream sensor. Another website says xxx-9F472-xxx. Even another website says "green plug" for Flex fuel (which is mine). Rockauto lists 3 different kinds (DY-1038, -1039, -1040). Reply from Rockauto to my email didn't help. Which one is for me? OEM is 11". Thanks.
Compression balance the old school way.

Disable the ignition. Listen carefully.
Crank the engine and listen to the starter as each cylinder goes by. The rhythm sould be the same on all 6. Any significant difference will be heard like a skip in the rhythm. To determine if a skip is valve or rings. Put a bit of oil in each spark plug hole. If it helps, it is rings. If not is valves.

-chart- the old coot
 

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3) Please help me select the right oxygen sensor. I used to think oxygen sensors are different only in the lead wire length. Actually, there are universal oxygen sensors that you can use for both banks, both up- and downstream.

I am looking for a genuine Ford part. One website says xxx-9G444-xxx is the upstream sensor. Another website says xxx-9F472-xxx. Even another website says "green plug" for Flex fuel (which is mine). Rockauto lists 3 different kinds (DY-1038, -1039, -1040). Reply from Rockauto to my email didn't help. Which one is for me? OEM is 11". Thanks.
You want the DY-1039 sensor on rockauto. It's 10.6" (271mm). The 1040 one is 15.5" long, but I don't know where this one would be used (flex fuel shouldn't make a difference). The 1038 is the downstream sensor and only differs by the harness color (blue for downstream vs. green for upstream sensors). Otherwise all the sensors are identical and could be used interchangeably if the wires were long enough since they all work the same way. The parts diagram probably shows the older sensor part numbers that have since been replaced by these three current sensors.
 

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Discussion Starter · #12 ·
Correct part ordered. Will report back when replaced.

chartmaker,
I trust old mechanics. But there aren't any around me. There are only pepboys and dealers in my area.
 
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